Sealing devices are typically used in applications, where there is a pressure difference on opposite sides of a wall, to reduce or eliminate an undesired gas flow through any apertures in the wall. One such application is in a fabric filter system, where the wall may delimit a filter plenary space. The filter plenary space contains hot, chemically aggressive gases at low pressure. If cold ambient air leaks into the filter plenary space, the interior gas temperature falls, possibly causing the interior gas to condense. Interior gas condensation is undesirable since often it tends to cause excessive corrosion. Therefore, seals or sealing devices used to prevent or reduce leakage of ambient air should be gastight. At the same time, the seal/sealing device may need to allow for a certain flexibility, since control of the controlled entity may require various movements of the control rod. Allowing for such movement makes sealing devices relatively complex and expensive, while compromising the sealing efficiency to some extent.
One option to solve this problem would be to make the control rod flexible or articulated to reduce or eliminate the need for sealing device flexibility. However, such a modification would render the control rod and the use of the control rod to control the controlled entity relatively more complex and costly.